1) Field of the Disclosure
The disclosure relates generally to composite structures and systems with radius fillers, and more specifically, to aircraft composite structures and systems with conductive radius filler systems to facilitate electrical conductivity, and methods of making the same.
2) Description of Related Art
Aircraft wings and fuselage structures have typically been made of metal materials which provide electrical conductivity and a current return to carry functional and fault currents and to handle electrostatic dissipation. Composite materials are increasingly being used in the manufacture of aircraft wings and fuselage structures, due to their high strength-to-weight ratios, corrosion resistance, and other favorable properties, and to improve performance and reduce the weight of the aircraft.
For example, aircraft wings may be formed of composite stiffened panel structures comprising composite wing skin panels, to which reinforcing stringers or stiffeners, spars, and ribs may be attached to improve the strength, stiffness, buckling resistance, and stability of the composite wing skin panels. Gaps or void regions may be formed by the radius of each curved piece of the reinforcing stringers, such as blade or T-shaped stringers, I-shaped stringers, J-shaped stringers, or other types of stringers, when they are attached or joined perpendicularly to composite wing skin panels. Radius fillers or “noodles” made of composite material and having a generally triangular cross-section may be used to fill the radius filler regions or noodle regions in order to provide additional structural reinforcement to such regions.
However, composite materials used to make composite aircraft wings, fuselage, or other aircraft structures, including composite radius fillers, typically have low or no electrical conductivity. Good electrical contact between composite aircraft wings, fuselage, or other aircraft structures, and metal fasteners used in such composite aircraft wings, fuselage, or other aircraft structures, is important to provide electrical conductivity and static dissipation, such as in the event of a lightning strike or other electrical event, and to provide adequate current return and current flow pathways.
Known dedicated conductive systems consisting of metal wires or similar metal structures may be added to composite aircraft wings, fuselage, and other aircraft structures to provide electrical conductivity and a current return. However, such known dedicated conductive systems may be heavy (i.e., hundreds of pounds of metal wires) and may add weight to the aircraft. Increased weight of an aircraft, for example, may result in increased fuel consumption, which, in turn, may result in increased fuel costs. In addition, such known dedicated conductive systems may be complex and difficult to install, which, in turn, may result in increased manufacturing time and increased labor costs.
Moreover, composite aircraft wings or other aircraft structures may include internal composite stringers, spars, and ribs that may have trimmed or cut edges. Gaps along such trimmed or cut edges, where composite wing skin panels meet the internal composite stringers, spars, and ribs, may be susceptible to “edge glow”, which is a plasma ejection or highly excited particle emission or ejection or spraying out of electrons at the trimmed or cut edges, resulting as a secondary effect of a lightning strike. Such edge glow may result in plasma ejection and may be a potential ignition source in fuel tanks or other areas within the aircraft composite wing.
Known systems and methods exist to prevent or mitigate edge glow in composite aircraft wings and other aircraft structures. Such known systems and methods include the application of sealants to cover the trimmed or cut edges of the internal composite stringers, spars, and ribs, and to cover metallic features, such as metal fasteners, on the aircraft composite wings. In addition, such known systems and methods include the use of fastener cap seals to cover metallic features, such as metal fasteners, on the composite aircraft wings or other aircraft structures.
However, such known sealants and fastener seal caps may be numerous in number and may add weight to the aircraft, which may result in increased fuel consumption, and, in turn, may result in increased fuel costs. Moreover, such known sealants and fastener seal caps may be time consuming and labor intensive to apply to the aircraft composite wings or other aircraft structures, which, in turn, may result in increased manufacturing time and increased labor costs.
Further, composite materials of aircraft composite wings may build up a charge from friction produced on the exterior of such aircraft composite wings, from refueling electrification, and from fuel sloshing in the fuel tanks of such aircraft composite wings. If electrical contact between the aircraft composite wings and metal fasteners in the aircraft composite wings is inadequate, the current from a lightning strike may not dissipate, may remain in the vicinity of a struck fastener and may be conducted into the substructure and possibly the fuel tank, where electrostatic discharge or sparking may occur, leading to a potential ignition source.
Known systems and methods exist to prevent or mitigate electrostatic discharge in aircraft composite wing fuel tanks and other aircraft composite structures. Such known systems and methods include the application of sealants and the use of fastener cap seals to cover metallic features, such as metal fasteners, in the aircraft composite wing fuel tanks to contain the electrostatic discharge in the fastened joint and prevent it from escaping into the fuel tank or other aircraft composite structures.
However, such known sealants and fastener seal caps may be numerous in number and may add weight to the aircraft, which may result in increased fuel consumption, and, in turn, may result in increased fuel costs. Moreover, such known sealants and fastener seal caps may be time consuming and labor intensive to apply to the aircraft composite wings or other aircraft structures, which, in turn, may result in increased manufacturing time and increased labor costs.
Accordingly, it is desirable to have and there is a need in the art for aircraft composite structures and systems with radius filler systems to facilitate electrical conductivity, and methods of making the same, that provide advantages over known structures, systems, and methods.